1. Field of the Invention
The present invention relates to hermetic compressors, more particularly, to an apparatus for separating lubricating oil from a mixture of gaseous refrigerant and oil in hermetic compressors.
2. Description of the Related Art
In general, hermetic compressors include a hermetic body which encloses a motor unit and a compressing unit. The hermetic compressor compresses a gaseous refrigerant input from an evaporator. At this time, the gaseous refrigerant changes its state from high temperature and low pressure into high temperature and high pressure. The compressed refrigerant, i.e., the refrigerant having a high temperature and a high pressure is discharged out of the compressor.
As shown in FIGS. 1 through 3, such a hermetic compressor includes a hermetic body 100 in which a motor unit 110 and a compressing unit 120 are installed at respective upper and lower portions thereof. The motor unit 110 enables the compressing unit 120 to suck-in a refrigerant, to compress the sucked-in refrigerant, and to discharge the compressed refrigerant.
The motor unit 110 includes a stator 111 and a rotor 112 which rotates depending on an electromagnetic relation with the stator 111. A crankshaft 113 is press-fitted in a through hole of the rotor 112.
The compressing unit 120 includes a cylinder 123 that provides a chamber for compressing the refrigerant input through a suction tube 121. A piston 124 is reciprocated in the cylinder 123 by the rotation of the crankshaft 113. A cylinder head 125 closes an end of the cylinder 123. Between the cylinder 123 and the cylinder head 125, a valve unit including a suction reed valve (not shown), a valve plate 126 and a discharge reed valve 127 is inserted. The suction reed valve, the valve plate 126 and the discharge reed valve 127 are used for respectively admitting refrigerant into the cylinder 123 and discharging the refrigerant out of the cylinder 123 after the refrigerant is compressed.
When power is supplied to the motor unit 110, the crankshaft 113 is rotated thereby to reciprocate the piston 124 in the cylinder 123. As a result, steps of sucking, compressing and discharging the refrigerant are carried out.
As shown in FIGS. 1 and 3, a refrigerant travels through the suction tube 121, a suction muffler 122, a suction chamber 125a of the cylinder head 125, and a suction hole 126a of the valve plate 126, successively. The refrigerant is then compressed by the piston 124.
Thereafter, the compressed refrigerant is passed through a discharge hole 126b and pushes open the discharge reed valve 127. The refrigerant is then discharged out of the body 100 through a discharge chamber 125b of the cylinder head 125, and a discharge tube 128, successively.
Generally, in a refrigeration cycle using such a compressor, a lubrication oil is mixed with the liquid refrigerant in order to lubricate mechanically removable parts. During the cycle, the mixture is passed through the evaporator wherein the liquid refrigerant, having a low temperature and a low pressure, is changed into a gaseous refrigerant. Thereafter the gaseous refrigerant is fed into the compressor. However, the lubrication oil contained in the refrigerant is still in its liquid state and is fed into the cylinder 123 of the compressor.
In other words, as shown in FIG. 3, the lubrication oil fed through the suction tube 121 together with the refrigerant is sucked along the internal side of a connecting spring 129 into the suction muffler 122. The sucked refrigeration oil is fed into the cylinder 123 through the valve 126 and is discharged through the valve 127.
However, the oil fed into the cylinder 123 of the compressor may reduce the efficiency of suction, compression and discharge of the gaseous refrigerant. This may result in a reduced refrigeration capacity of machineries using the compressors.
In addition, oversupply of the oil through the valves 126 and 127 may cause a valve unit failure.